Re: [lkcd-devel] Re: What's left over.

Pavel Machek
2002-11-10T11:43:26Z

Hi!

> > Yes, we are putting [MCORE] in as one of the alternative dump targets
> > available.
>
> Great !
>
> > Its not quite ready yet and we need something like kexec to be
> > available which we can use on Intel systems to achieve the softboot
> > (the acceptance status of that still doesn't seem to be clear),
>
> Yes, I've just checked with Eric, and he hasn't received any
> indication from Linus so far. I posted a reminder to linux-kernel.
> I'd really hate to see kexec miss 2.6.
>
> > Why do we even consider the other options when we are doing
> > this already ? Well, as we discussed earlier there's non-disruptive
> > dumps for one, where this wouldn't work.
>
> But they're very different anyway, aren't they ? I mean, you could
> even implement them (well, almost) from user space, with today's
> kernels.
>
> > The other is that before overwriting
> > memory we need to be able to stop all activity in the system for certain
> > (system may appear hung/locked up) and I'm not fully certain about
> > how to do this for all environments. Maybe an answer lies in
> > rethinking some parts of the algorithm a bit.
>
> This is certainly the hairiest part, yes. I think we have about
> four types of devices/elements to worry about:
>
> - those that just sit there, and never talk unless spoken to
> - those that may generate interrupts
> - those that DMA if you ask them nicely
> - those that DMA when they feel like it (e.g. copy an incoming
> network packet to the next buffer in the free list)
>
> The latter are the real problem. I see the following possibilities
> for dealing with them:
>
> - faith-based computing: pray that nothing bad will befall your
> system :-)
> - de-activate them individually. There should be a lot of work
> that can be shared with power management. And that's one of
> the reasons why I think the memory target should be available
> early, or convergence will take forever.

I have very similar problem in swsusp (need to deactivate DMA
devices), and driverfs^H^H^H^H^Hsysfs framework seems to be suitable
for that.

Pavel
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